Polymers having carboxy or anhydride groups may be effectively cured or crosslinked by treating the polymer with a .beta.-hydroxyalkylamide or a polymer containing .beta.-hydroxyalkyamide functionality, as disclosed in U.S. Pat. Nos. 4,076,917; 4,101,606; 4,115,637; 4,138,541; 4,727,111 and 4,801,680. Examples of suitable acid or anhydride monomers which can be incorporated into the polymer backbone and crosslinked with .beta.-hydroxyalkylamides include: unsaturated monocarboxylic acids; such as acrylic acid, methacrylic acid, crotonic acid and the like; unsaturated dicarboxylic acids such as maleic acid, 2-methylmaleic acid, itaconic acid, 2-methylitaconic acid, alpha,beta-methyleneglutaric acid and the like; unsaturated anhydrides such as maleic anhydride, itaconic anhydride, acrylic anhydride, methacrylic anhydride and the like; and amorphous carboxylic acid-group containing polyesters formed by the condensation reaction of aliphatic polyols and/or cycloaliphatic polyols with aliphatic and/or aromatic polycarboxylic acids and anhydrides.
The synthesis of .beta.-hydroxyalkylamides and their use as crosslinkers, such as for example in the preparation of thermosetting coatings, was examined in: B-Hydroxyalkylamides, Low Polluting Crosslinkers For Carboxyl Containing Polymers, J. Lomax and G. Swift, Journal of Coatings Technology, Vol. 50, No. 643 (Aug. 1978) pages 49-55; Esterification of N(2-Hydroxyalkyl)Amides, Z. W. Wicks and N-C. Chiang, Journal of Coatings Technology, Vol. 54, No. 686 (Mar. 1982) pages 27-31; and Reaction of N-(2-Hydroxyethyl)Amido Compounds, Z. W. Wicks, M. R. Appelt and J. C. Soleim, Journal of Coatings Technology, Vol. 57, No. 726, (July 1985) pages 51-61.
None of these references, however, disclose or suggest thiol-terminated hydroxyamides or their use as chain transfer agents in polymerization reactions.
It was an object of the present invention to determine whether a thiol-terminated hydroxyamide, as for example a thiol-terminated .beta.-hydroxyalkylamide, could be prepared and used as a chain transfer agent for the preparation of hydroxyamide-functional polymers or oligomers.
In addition, it is a further object of the invention to determine whether such hydroxyamide-containing polymers and oligomers could be subsequently reacted with acid-containing monomers or polymers to form block and graft copolymers.
For the purpose of the present disclosure the term "oligomer" shall refer to low molecular weight polymers which can function as monomers in subsequent polymerization reactions with other monomers or polymers. These functional oligomers are also referred to in the art as "macromers" or "macromonomers". The weight average molecular weight of these oligomers is typically in the range of from as low as about 300 to as high as about 5000.